GBU-38

Hello everyone. I'm messing ariund with weapons to get a good feel for them as I left BMS behind abd want to fly DCS. I'm having trouble with JDAM. I create SPI in TGP, when I go to release, as soon as the marker starts to rotate I hold pickle and nothing happens. I don't get MAN release cue until after I'm almost flying over target.

What am I doing wrong ? When I do get them off the rail, they're way too long and miss by several feet.

Please post a track

Yup. A track is worth a thousand words.

Or at least a screenshot of the moment when you want to pickle.

Hello everyone. I'm messing ariund with weapons to get a good feel for them as I left BMS behind abd want to fly DCS. I'm having trouble with JDAM. I create SPI in TGP, when I go to release, as soon as the marker starts to rotate I hold pickle and nothing happens. I don't get MAN release cue until after I'm almost flying over target.

 

 

 

What am I doing wrong ? When I do get them off the rail, they're way too long and miss by several feet.

It seems as the jdam have not received the correct SPI? Also make sure you are in Ccrp mode in the hud and that the jdam is correctly set as ccrp mode in the weapons profile page.

Enviado desde mi SM-G950F mediante Tapatalk

As 'falcon_120' noted above, sounds like the GBU isn't getting the proper SPI.

Below are the 2 procedures that i follow, mainly the first one, sometimes the second if timing is crucial (target of opportunity or other conditions).

Also check that your INS is properly aligned, EGI mode is ON and EAC enabled.

In the DSMS page you should see your GBU as ready (i think the indications is RDY)

--- Correct procedure:

1. Designate the target via any of the sensors (usually TGP)

2. Create a MarkPoint via TMS-Right short

3. With CDU set to MKPT mode, select the correct MarkPoint (HUD SOI then DMS Up/Down)

4. Make the MarkPoint SPI via TMS-Up long (check lower-left of the HUD for STEER indication) EDIT: It's actually TMS Aft Long

5. Align and drop the bomb

--- Not-so-correct-but-faster procedure:

1. Designate the target via TGP

2. Lase 1 or 2 seconds for correct ranging and position fix

3. Make the TGP SPI via TMS-Up long when TGP is SOI

4. Align and drop the bomb

That`s the way it goes.

CCRP-GBU12.trk

What am I doing wrong ?

Like the others said, please post a track.

Are you creating a markpoint and making that markpoint(TMS-right) the SPI through a TMS-UP long command?

That suggestion leaves out so many required steps, I'm wondering if OP will be any wiser after reading it. Plus see below...

--- Correct procedure:

1. Designate the target via any of the sensors (usually TGP)

2. Create a MarkPoint via TMS-Right short

3. With CDU set to MKPT mode, select the correct MarkPoint (HUD SOI then DMS Up/Down)

4. Make the MarkPoint SPI via TMS-Up long (check lower-left of the HUD for STEER indication)

All around good advice! :thumbup:

But in Step 4 above, which sensor should be SPI Generator to set STEER as SPI Generator with TMS Forward Long?

I guess you meant TMS Aft Long?

--- Not-so-correct-but-faster procedure:

1. Designate the target via TGP

2. Lase 1 or 2 seconds for correct ranging and position fix

3. Make the TGP SPI via TMS-Up long when TGP is SOI

4. Align and drop the bomb

Step 2 doesn't make any sense in this case.

The SPI isn't "made" or "created", it's generated. With TGP as SPI Generator, the SPI keeps getting generated where ever the TGP looks at. So lasing for a few moments while the TGP remains SPI Generator just means that for those 1 or 2 seconds, the aircraft might have generated a slightly more accurate SPI, but that's really no good if you don't release the weapon, or create a markpoint, while the laser is still lasing. :smartass:

I tested on my machine and all seems ok.

A bit OT here, but do you think there's any chance the manual could be updated?

The description of "making" or "creating" SPIs has been confusing the heck out of people for as long as I can remember (ran into that same trap myself until someone with much more knowledge pointed me to the error in my assumptions).

I believe the correct term for TMS Forward Long would always be: Set SPI Generator.

I can open a new wishlist thread if you think that makes sense.

PS: Congrats on making your job official. Not that you haven't been a community manager for as long as I can remember, official title or not. :)

That`s the way it goes.

Sorry, can't play the track because of a required mod; something about NATO vehicles.

All around good advice!

 

But in Step 4 above, which sensor should be SPI Generator to set STEER as SPI Generator with TMS Forward Long?

 

I guess you meant TMS Aft Long?

Yes sorry, should have been TMS Aft Long to reset whatever is SPI to the "default" STEER SPI (editing the post right away!)

Step 2 doesn't make any sense in this case.

 

The SPI isn't "made" or "created", it's generated. With TGP as SPI Generator, the SPI keeps getting generated where ever the TGP looks at. So lasing for a few moments while the TGP remains SPI Generator just means that for those 1 or 2 seconds, the aircraft might have generated a slightly more accurate SPI, but that's really no good if you don't release the weapon, or create a markpoint, while the laser is still lasing

Once you "point" something with your TGP, the actual distance between you and whatever the target is, is being calculated with a mix of your position, the target's estimated position based on size and distance ranging via the focus function. This gives an approximation of the target's position. Not sure if in DCS is actually modeled but lasing should "accurately fix" the generated point by making sure the distance is actually correct instead of being an approximation.

Technically you “SET” SPI using TMS UP LONG on whatever is SOI.

Once you "point" something with your TGP, the actual distance between you and whatever the target is, is being calculated with a mix of your position, the target's estimated position based on size and distance ranging via the focus function.

Are you sure about that?

So far I was under the impression that the aircraft includes a terrain elevation database, and calculates the target position as the position where TGP line of sight intersects with the ground. As a result, any dynamic object (car, tank, truck, tent, and so on) would be excluded from the calculation.

With the laser, the exact distance to the object is measured and the measurement should become more accurate.

Not sure if in DCS is actually modeled but lasing should "accurately fix" the generated point by making sure the distance is actually correct instead of being an approximation.

Yup, I'm pretty sure that is indeed modeled.

But my point was something else anyway. If you lase a spot for an accurate measurement and then stop lasing, the accurate measurement goes away immediately, and the calculation goes right back to LOS ground intersection. At least that is my current understanding of how the system works.

So unless you perform an action while the laser is being fired, it doesn't do any good in terms of positional accuracy. It's like saying "Hey, I knew the exact position of that target at some point in the past. But I didn't take notes, and now I'm back to knowing its approximate position". :smartass:

Technically you “SET” SPI using TMS UP LONG on whatever is SOI.

Agreed. But would you say that "Set SPI Generator" is wrong, or is badly worded? I think "Set SPI Generator" is more accurate and also conveys the proper idea, and is therefore my preferred wording.

Edit: @Bignewy here we go.

So far I was under the impression that the aircraft includes a terrain elevation database, and calculates the target position as the position where TGP line of sight intersects with the ground. As a result, any dynamic object (car, tank, truck, tent, and so on) would be excluded from the calculation

Yes exactly.

That's why you would need to lase the actual "dynamic object" to have a very precise position/elevation calculation (see my point below)

...If you lase a spot for an accurate measurement and then stop lasing, the accurate measurement goes away immediately, and the calculation goes right back to LOS ground intersection. At least that is my current understanding of how the system works...

I'm not 100% sure as my knowledge comes from just what i've read over the years on the web, though it should be that once you lase you "keep" the corrected position until you move the TGP again, at which point it goes back to LOS/Focus calculations

I'm not 100% sure as my knowledge comes from just what i've read over the years on the web, though it should be that once you lase you "keep" the corrected position until you move the TGP again, at which point it goes back to LOS/Focus calculations

I just set up a very simple mission with some static objects and switched on the active pause when I was just at the gap where the TGP would show me (for instance) a range of "L T 5.9". Then while lasing it read "(Flashing) L L 5.8". As soon as I let go of the laser, the range readout went right back to "L T 5.9".

I'm quite certain the object distance/position given by the laser is only valid as long as the laser is actually firing.

When TGP sets a SPI, it is a calculation based on several sensors and the data cartridge would contain a map pack for the area containing vector/raster, moving map and elevation and the TGP gimbal sensors provide slant angle etc. All this gives us a rough but fairly accurate (I'm guessing to within 10m)

I would assume IRL when TGP is SPI, and uses the laser for more precise range finding, the SPI data would get updated to reflect this.

In game we do have some issues with the laser rangefinder and I do not know for a fact if this (updating SPI more accurately actually happens.) I do almost always lase prior to firing a JDAM and it usually works. All early DCS A10C documentation/videos and training did state that using laser does indeed give a more precise SPI data point.

It would really take someone from ED to come out and substantiate this claim.

I generally have the laser firing when I make a mark point with the TGP looking at the base of the target.

If using TGP SPI, make sure the laser is firing when you drop if you want to be realistically employing. I believe in game the accuracy of your grids from TGP SPI is not affected by laser usage, which honestly is fine in a game.

IRL STPT SPI and TGP SPI are realistically the only SPIs to drop on, but in theory you could use others. Both of Kid18120's procedures are doctrinally correct, although now with later A-10 Suites its further refined because you are able to copy a recently made markpoint to an existing steerpoint. By default, steerpoints 1-10 in the A-10 are designed to be target steerpoints labeled T1, T2, etc. The current procedure is to create the markpoint, put 1-10 in the scratchpad, and then click OSB 8 or 9 (the one with the basketball looking icon) to copy the grids you generated to a target steer. This is called "refining and updating" and you are able to very quickly create targetable grids for steerpoints.

This is powerful because I could refine and update T1-4, four warehouses within close proximity, and hit them all on one pass. If I had 4 GBU's I could "pickle step pickle", or drop on T1, switch to T2 and drop, etc. Recently with Suite 9 we have the ability to put multiple targets in a list, press the pickle button once, and have multiple bombs hit multiple targets simultaneously.

-Habu

In game we do have some issues with the laser rangefinder

Which issues are these?

[...] and I do not know for a fact if this (updating SPI more accurately actually happens.)

I think that should be fairly easy to test in DCS.

When I ran such a test 2 days ago, the result seemed fairly conclusive in that DCS does indeed generate a more accurate SPI while the laser is firing.

I do almost always lase prior to firing a JDAM and it usually works.

You don't drop JDAMs on Steerpoints?

Not trying to criticize. I was just under the impression that that was a standard procedure IRL in order to minimize the risk of TGP f* ups and SPI confusion.

Both of Kid18120's procedures are doctrinally correct, although now with later A-10 Suites its further refined because you are able to copy a recently made markpoint to an existing steerpoint. By default, steerpoints 1-10 in the A-10 are designed to be target steerpoints labeled T1, T2, etc. The current procedure is to create the markpoint, put 1-10 in the scratchpad, and then click OSB 8 or 9 (the one with the basketball looking icon) to copy the grids you generated to a target steer. This is called "refining and updating" and you are able to very quickly create targetable grids for steerpoints.

Interesting!

So waypoints 1 to 10 are kind of reserved in newer A-10Cs? Does that mean flightplan waypoints are automatically numbered 11 to X (whatever the max amount is)?

This is powerful because I could refine and update T1-4, four warehouses within close proximity, and hit them all on one pass. If I had 4 GBU's I could "pickle step pickle", or drop on T1, switch to T2 and drop, etc.

Okay, so the difference between that procedure and DCS is that in DCS, our target waypoints are not necessarily in sequence and we'd have to put them into a flight plan in order to make sure we'd get the correct sequence?

Other than that, the steps in DCS still seem to be quite spot-on. :)

Recently with Suite 9 we have the ability to put multiple targets in a list, press the pickle button once, and have multiple bombs hit multiple targets simultaneously.

Now that sounds like a nice to have feature. :)

I think that should be fairly easy to test in DCS.

 

When I ran such a test 2 days ago, the result seemed fairly conclusive in that DCS does indeed generate a more accurate SPI while the laser is firing.

But you stated the SPI does NOT remain updated once you stop the laser. Either way it would take hundreds of tests with and without laser to actually come up with a valid conclusion.

So far from what I see, the TGP accuracy is enough to drop any bomb on target.

Recently with Suite 9 we have the ability to put multiple targets in a list, press the pickle button once, and have multiple bombs hit multiple targets simultaneously.

OMG that'd be lovely to have on our old man (suite 3 i believe?)